1. Field of the Invention
The present invention relates to a forming apparatus for manufacturing a curved panel by shaping a flat metal sheet to be curved, and more particularly, to a multipoint stretch forming apparatus enabling individual clamping control for manufacturing a curved panel, wherein both ends of a sheet are stretched to match to the shape of a curved panel by using a plurality of clamps each individually controlled.
2. Description of the Related Art
Generally, curved metal panels in various shapes are used for the hull of a ship, the fuselage of an airplane, the exterior panel of a building.
When a press die is used to mass-produce a curved panel in a typical shape which is a fixed curve shape, like a globular shape or an arc shape, it increases the improvement of workability and productivity.
However, in the case of a curved panel in an atypical shape having multi-dimensional curve shapes, it is very difficult to manufacture it using a press die. Further, when the demand for a particular curved panel is low, a production cost is high due to the die expense.
Patent document 1, below, discloses an apparatus for forming components for an airplane. This apparatus comprises: a top punching member positioned to move vertically by a hydraulic and/or pneumatic device; a bottom die having a processing surface with a number of flat sections, a number of protruding sections and a number of groove sections on its upper side, wherein a workpiece to be processed is positioned on the processing surface; and a number of pressing blocks for a secondary process, positioned on the workpiece so as to be positioned at the groove sections of the bottom die.
To form curved panels for an airplane by using a particular die, such as the apparatus for forming components for an airplane of patent document 1, many dies are needed to form the curved panels in various shapes. Accordingly, the apparatus for forming a curved panel like patent document 1 is not proper to form curved panels in a small quantity batch production.
Patent document 2, below, discloses a multipoint variable press-type apparatus for forming a curved panel. This apparatus comprises: a base with a forward and backward guide rail and a right and left guide rail positioned in the horizontal direction; a bottom punch module positioned on the base, with a number of punches to hold and support a curved panel; a top punch module with a number of punches vertically movable by a hydraulic system; a first supporting punch module positioned at one side of the top punch module, with a number of punches vertically movable by a hydraulic system; and second supporting punch modules positioned at right and left sides of the bottom punch module, with a number of punches vertically movable by a hydraulic system.
Patent document 3, below, discloses a multipoint stretch-type apparatus for forming a shape steel with a curved surface. This apparatus comprises: a stretching section applying tension in the state that both ends of the steel to be shaped are supported by clamps; a formation molding section applying a shear force to the steel under the stretching section; and a controlling section forming a curved surface of curvature being set at a yield point of the steel, by connectively controlling the stretching section and the formation molding section.
Patent document 4, below, discloses a method for manufacturing a panel having a multi-dimensionally curved surface. In this patent document, top and bottom dies are variably symmetrically set as a specific shape of a particular multi-dimensionally curved surface, using a number of multipoint molding pins. In the state that a metal sheet to form the multi-dimensionally curved surface is secured on the top surface of the bottom die forming the specific shape of the multi-dimensionally curved surface, a number of stretch forming apparatuses pull both ends of the metal sheet with a force exceeding a plastic point and a yield point of the metal sheet, to primarily form the multi-dimensionally curved surface in the same shape formed on the top surface of the bottom die. Then, the top die moves down to press the metal sheet stretched in the shape formed on the top die as the shape is.
All techniques disclosed in patent documents 2 through 4 are to efficiently form an atypical shape steel or atypically curved panel in small quantity, by using variable dies.
Patent document 5, below, discloses an elongating, forming and processing machine and method and patent document 6 discloses an apparatus and method for forming panels into complex curved shapes.
The apparatus disclosed in patent document 6, below, comprises a variable displacement tension bar including a number of pull tabs and enabling each pull tab to be independently controlled.